A chirp signal or chirp can refer to a frequency modulated (FM) signal. A chirp signal can be used in radar applications, such as determining an object's range. A chirp signal has a frequency that varies over a fixed period of time. When a desired frequency as a function of time takes on a sawtooth ramp, it can be referred to as a sawtooth chirp. A sawtooth chirp may be generated using a ramp generator and/or in a phase-locked loop.
Phase-locked loops (PLLs) are closed loop systems for locking the phase of a reference signal with an oscillator. A PLL can be designed to have a specific type (e.g., type-I, type-II, or higher) and a specific order (e.g., 1st order, 2nd order, or higher). In system theory, the type can refer to the number of integrators within the loop and the order can refer to the degree of the denominator in the PLL system transfer function. Both the order and the type can impact functionality of a PLL suitable for reliably generating sawtooth ramps.